green@rensselaer is a new series of articles, blog entries, podcasts, and videos highlighting issues and topics related to sustainability, energy, and the environment. The series will examine the research, student initiatives, administrative efforts, and individuals at Rensselaer who are striving in different ways toward the shared goal of reducing society’s impact on the environment.

Just a few years ago, most conversations Christian Wetzel had about his research began with a quick explanation of LEDs.

More recently, however, he’s noticed that the mention of LEDs  light-emitting diodes  no longer prompts puzzled looks. He rarely has to delve into the elevator pitch about LEDs needing only a fraction of the energy required by conventional light bulbs, or mention that LEDs contain none of the toxic heavy metals used in the newer compact fluorescent light bulbs. He no longer has to sell the idea that LEDs are incredibly durable and long-lived.

The virtues of sustainability and efficiency are now so engrained in the public consciousness, Wetzel said, that he can usually skip over the nuts and bolts of solid-state lighting and instead launch right into his work on developing a high-performance, low-cost green LED.

“Going green means different things to different people. For most, it means being more conscious about the environmental and global impacts of one’s actions. For companies, going green also means making a profit by selling equipment and services that allow one’s customers to be more efficient and reduce costs,” said Wetzel, professor of physics and the Wellfleet Professor of Future Chips at Rensselaer. “I’m doing both of those, but I’m also trying to make an LED that literally shines green light.”

First discovered in the 1920s, LEDs are semiconductors that convert electricity into light. When switched on, swarms of electrons pass through the semiconductor material and fall from an area with surplus electrons into an area with a shortage of electrons. As they fall, the electrons jump to a lower orbital and release small amounts of energy. This energy is realized as photons  the most basic unit of light. Unlike conventional light bulbs, LEDs produce almost no heat.

The color of light produced by LEDs depends on the type of semiconductor material it contains. The advancement of LED technology, Wetzel said, has followed a specific progression. The very first LEDs were red, and not long thereafter researchers tweaked their formula and developed some that produced orange light. Next in line, after considerable research efforts and some key breakthroughs, were blue LEDs, which can easily be found today as blue light sources in mobile phones, CD players, laptop computers, and other electronic devices.